Note: Descriptions are shown in the official language in which they were submitted.
1043186
SPECIFICATION
This invention relates to method and apparatus for elec-
trostatically depositing powder on continuously moving strip, par-
ticularly metal powder on continuously moving metallic strip.
Apparatus has been provided in the past for electrostat-
ically depositing metal powder on continuously moving metallic
strip. For example, U. S. Patent 3,575,138 provides an elongated
chamber through which metallic strip is continuously moved and a
single nozzle for introducing a cloud of metal powder into the
chamber where the particles of metal powder are charged and moved
toward and onto the strip under the influence of an electrostatic
fiéld. Because of the characteristics of flow of an aerosol of
metal powder and compressed gas such as air to and through a nozzle -
and the characteristics of the discharge from the nozzle, apparatus
employing a single nozzle for introducing a cloud of metal powder
into an electrostatic deposition zone are not capable of electro-
statically depositing metal powder with sufficient uniformity trans-
versely and longitudinally of the metallic strip when the width of
the strip exceeds 10 inches, particularly when the width of the
metallic strip is 20 to 40 inches.
It is accordingly an object of the present invention to
provide a process and apparatus for electrostatically depositing
metal powder on continuously moving metallic strip of a width
greater than 10 inches, particularly strip having widths of 20 to
40 inches, in which a substantially uniform coating of metallic
powder is deposited on the strip, transversely and longitudinally,
for a wide range of strip speeds and metal powder coating weights.
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Accordingly, there is provided in accordance with one aspect of
the present invention apparatus for applying a coating of metal on continu-
ously moving metallic strip of width greater than 10 inches comprising
an elongated housing of non-electrically conducting material having an
entrance opening and an exit opening and defining an elongated passageway
extending between the entrance opening and the exit opening,
means for continuously moving strip material through the elongated
passageway of the housing along a path in a direction from the entrance open-
ing to the exit opening in out-of-contact relation with the material of the
housing,
means located in the housing for charging particles introduced into the
passageway of the housing and for producing an electrostatic field in the
passageway for moving charged particles in a direction toward the strip pass-
ing through the passageway,
and means for introducing a cloud of powder into the passageway at its
entrance opening generally in the direction of movement of the strip through
the passageway,
the last-named means including a plurality of fixed nozzles spatially
positioned transversely of the path of movement of the strip through the
elongated passageway,
and means for feeding to each of the nozzles a pressurized aerosol
including a gas and powder.
In accordance with a further aspect of the present invention there
is provided method of applying metal powder to continuously moving metallic
strip of a width greater than 10 inches comprising the steps of
continuously passing strip material through an electrostatic deposition
zone in a direction from the entry end of the zone to the exit end of the
zone ~
introducing a plurality of clouds of powder into the zone at its entry
end generally in a direction corresponding to the direction of movement of
the strip through the zone,
the areas of the clouds of powder as introduction into the zone ~:~
lying in a common plane perpendicular to the direction of movement
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of the strip material through the zone and the area of the clouds diverg-
ing transversely of the strip material as the clouds move in the direction
of strip movement, and
each of the clouds ~eing introduced into the zone at spaced
areas extending transversely of the strip material such that the marginal
portions of adjacent clouds intermix in a region of the zone spaced in
a direction of strip movement from the c~mmon plane.
The invention is illustrated by way of example with reference
to the accompanying drawings wherein:
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Fig. 1 is a diagrammatic view in side elevation and par-
tially in section of a coating apparatus constructed in accordance
' with the principles of the present invention;
Fig. 2 is a diagrammatic view in plan and partial~y in
section of the coating apparatus shown in Fig. l;
Fig; 3 is an enlarged view partly in section of a part of
the apparatus shown in Figs. 1 and 2;
Fig. 4 is an enlarged view in plan and partly in section
of a portion of the apparatus shown in Fig. l;
Fig. 5 is a view in section taken along the line 5-5 of
Fig. 4;
Fig. 6 is a view in section taken along the line 6-6 of
Fig. 5;
Fig. 7 is a graph showing the uniformity of coating weight
on metal strip obtained when practicing the present invention;
Fig. 8 i9 another graph showing the uniformity of coating
weight on metal strip obtained when practicing the present invention;
Fig. 9 is a further graph showing the uniformity of coat-
ing weight on metal strip obtained when practicing the present
invention;
Fig. 10 is a chart illustrating measured coating weights ,~
of deposited metal powder when practicing the invention according
to Example I;
Fig. 11 lS a chart illustrating measured coating weights
of deposited metal powder when practicing the invention according
to Example II; and
Fig. 12 is a chart illustrating measured coating weights
of deposited metal powder when practicing the invention according
to Example III.
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1043186
- Figs~ 1 and 2 of the drawings disclose apparatus embody-
ing the principles of the present invention for applying a uniform
coating of metal powder on continuously moving metallic strip with
means for wetting the strip prior to the metal powder deposition
and for heat treatment of the strip having the metal powder deposited~
thereon. It is to be understood that the principles of the present
invention may be embodied in dissimilar apparatus which provides
for different treatment of the strip before and after the metal
powder is deposited.
As shown in Figs. 1 and 2, the apparatus includes an un-
coiling device 10 supporting a coil 11 of metallic strip 12 such as
steel strip. The strip leaves the coil 11 and moves through a strip
wetting device 13 which functions to controllably wet the top sur-
face of the strip for metal powder adherence to the strip. The
wetted strip then moves through an electrostatic coating zone 14
where a coating of metal powder is deposited on the top surface of
the strip, as viewed in the drawing.
The strip with deposited metal powder then moves through
a heat treating furnace 15 and then to a coiling device 17 for
coiling the coated strip in coil 18. The uncoiling device 10 and
the coiling device 17 may be of conventional construction capable
of moving the strip through the apparatus at a controlled speed and
under required tension. The heat treating furnace 15 also may be
of conventional construction such as an infrared furnace.
The electrostatic coating zone 14 is defined by an elon-
gated housing 19 constructed of electrically insulating material and
having a strip entry opening 20 and a strip exit opening 21. Means
are provided for charging particles of metal powder within the zone
14 and for producing an electrostatic field within the zone 14 for
10431~6
- moving charged particles of metal powder in a direction toward the
top surface 22 of the strip. Such means is shown in the form of a
plurality of wires 23 extending transversely of the strip 12, spaced
from each other in the direction of movement of the strip and dis-
posed in a plane spaced from and parallel to the top surface 22 of
the strip. The wires are so supported by structure 24 of non-in-
sulating material located within the housing 19. The wires 23 are
continuously char~ed with a potential of one polarity, such as
positive, from power source 25 and the strip 12 is maintained at
the opposite potential such as by connection 26 to ground. Excess
metal powder that may accumulate within the housing 19 downstream
of the electrostatic coating zone 14 in the direction of strip
movement may be removed by conduits 27 which communicate with a
vacuum source and metal powder separator-collector 28. Also, con-
duits 29 connected to a source of vacuum, not shown, extending ;
transversely of the strip and located above and below the strip
and having openings facing the strip, collect excess powder and
minimize the flow of metal powder through the exit end 21.
In accordance with the principles of the present inven- ~
20 tion, a cloud of metal powder is introduced into the coating zone `~ -
14 by means of a plurality of discharge nozzles located at the
entrance end 20 of the housing 19. As described in detail below,
the discharge nozzles are so constructed and are so positioned rela-
tive to each other and to the strip so that a cloud of metal powder,
that is of substantially uniform density as to the metal powder ;
transversely and longitudinally of the strip, is continuously
maintained in the coating zone 14 so as to obtain under the influ-
ence of the electrostatic field a continuous application of metal
powder to the surface 22 of the strip that is of substantially
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uniform weight transversely and longitudinally of the strip. Four
discharge nozzles 30, 31, 32, and 33 are shown; however, it is to
be expressly understood that the principles of the present invention
may be employed using any number of discharge nozzles greater than
two depending upon variables including the width of the strip being
processed. Each of the discharge nozzles is fed with a pressurized
aerosol composed of metal powder and air or an inert gas produced
by a separate blower, such as blowers 34, 35, 36, and 37, respect-
ively, through a pipe section 38 and a tapered transition section
39. The blowers may be of any conventional construction capable of
providing the flow rates and velocities required and each is driven
by a variable speed motor 40. The inlet to each of the blowers 36,
37, 38, and 39 is continuously fed with measured quantities of metal
powder from hoppers 41, 42, 43, and 44 and associated conduits 45,
46, 47, and 48, respectively, as well as an inert gas such as air
which may also be controlled. A suitable arrangement for this
purpose is shown in Fig. 3 in relation with blower 36 and hopper 41.
As shown, the conduit 45 extends through the inlet opening 49 of the -;
blower 36 and terminates in communication with the cavity 50 of the
blower and a metal powder feed screw 51 is located within the
conduit 45 and in communication with the powder in the hopper 41 to
transfer metal powder to within the cavity 50 of the blower. The
feed screw 51 is driven by a variable speed motor 52 to continuously
feed controlled amounts of metal powder into the blower. The inlet
opening 49 may be shrouded by ductwork 53 which communicates with a
gas inlet conduit 54 provided with an adjustable valve 55 to
control the mass of gas entering the blower.
As shown more clearly in Figs. 5, and 6, the nozzles
30, 31, 32, and 33 each include spaced planar sidewalls 60 which
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convergingly taper in a longitudinal direction and a planar top
portion 61 and a spaced planar corresponding bottom portion, not
shown, both of which divergingly taper in a longitudinal direction
to provide an elongatedrectangular or slit-shaped discharge opening
62 the area of which corresponds to the area of the opening in the
feed conduit 38, the taper of the sidewalls and the top and bottom
portions being in the direction of strip movement. The nozzles 30,
31, 32, and 33 are supported by a transverse member 63, having
vertical supports not shown, with their discharge openings 62
facing in a direction toward the charging wires 23 and lying in a
common plane perpendicular to the direction of movement of the strip
12 and located within the housing 19 inwardly of the inlet 20.
Also, the nozzles are mounted with the long dimension of the slit-
shaped discharge opening 62 lying in a common plane parallel to and
spaced above the path of the strip 12. The nozzles 30, 31, 32, and
33 are symmetrically positioned relative to the width of the strip
12 and adjacent nozzles are equally spaced transversely of the di-
rection of strip movement. Preferably, a portion of the discharge
opening of the outboard nozzle 30 extends transverse~y beyond the
edge 64 of the strip and a portion of the discharge opening of the
other outboard nozzle 33 extends transversely beyond the other
edge 65 of the strip.
It has been discovered that in order to continuously
provide a cloud of powdered metal in the electrostatic coating
zone 14 so characterized that the metal powder electrostatically
deposited on the strip will be of substantially uniform weight
transversely and longitudinally of the strip, certain relationships
are required between the width of the strip and the transverse
spacing of adjacent nozzles and between the width of the strip and
1043~86
- the long dimension of the slit-type discharge openings. In parti-
cular, the relationships are:
(1) the long dimension of the slit-type discharge openings should
not be greater than one-fourth the width of the strip, (2) the
space between nozzles should not be greater than one-half the long
dimension of the slit-type discharge openings, and (3) the sum (i)
the combined long dimension of the slit-type discharge openings of
all of the nozzles and (ii) the total spacing between adjacent
nozzles, should not be less than the width of the strip. It has -
been discovered that satisfaction of these relationships makes
possible the electrostatic deposition of metal powder substantially
uniformly on metallic strip throughout ranges of coating weights
and strip speeds. These relationships have also been found to be
applicable to nozzles tapered no greater than 15 which is the
maximum taper that precludes metal powder sticking to and accumu-
lating on the inside planar surfaces of the nozzles thus making it
possible to obtain the desired uniformity of metal powder deposition
with nozzles of reasonable length.
When a pressurized aerosol of metal powder and gas is
fed to a nozzle that is divergingly tapered to provide a slit-type
discharge opening, the discharge from the nozzle, as viewed in a
plane parallel to the long dimension of the discharge opening, will
diverge upon the front of the discharge from the nozzle moving away
from the discharge opening as represented by the broken lines a
and _ associated with the nozzles 30, 31, 32, and 33 of Fig. 4.
The front of the discharge, that is, the discharge as viewed in a
plane parallel to the plane of the discharge opening, immediately
upon leaving the discharge opening of the nozzle will include a
center portion, extending equally from both sides of a plane
10431Y6
perpendicular to the long dimension of the discharge opening and
passing through its mid-point, in which the density of metal powder
will be substantially uniform, and side portions extending with
decreasing metal powder density to both ends of the discharge open-
ing. As the front of the discharge moves away from the discharge
opening, the center portion of substantially uniform metal powder
density will comprise a progressively decreasing percentage and
the side portions of outwardly varying metal powder density will
comprise a progressively increasing percentage of the total trans-
verse dimension of the discharge. In addition, with a nozzle havinga discharge opening of a greater transverse dimension and with the
other dimension being smaller, the center portion of the discharge
of substantially uniform metal powder density comprises a relatively
less percentage of the transverse dimension of the discharge when
the front is at the discharge opening and such percentage decreases
as the front moves away from the discharge opening. Notwithstanding
the foregoing, the present invention obtains a cloud-of metal pow-
der in the electrostatic deposition zone, of substantially uniform
metal powder density, which extends transversely of the strip
throughout its width as well as an appreciable distance in the
direction of strip movement. This is accomplished in accordance
with the present invention by the use of stationary nozzles in
specific relation to each other and to the strip material. The
relationship is such that the patterns of the discharge from the
nozzles, as represented by lines a and b of Fig. 4, overlap between
adjacent nozzles in a region beyond the plane of the discharge
openings 62 which extends a substantial distance in the zone 14
in the direction of movement of the strip so that the discharges
of all of the nozzles present a combined front of substantially
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uniform metal powder density extending transversely longitudinally
of the strip. The outboard nozzles 30 and 31 are preferably posi-
tioned so that their discharge openings extend outwardly beyond the
edges 64 and 65 of the strip, respectively, to aid in obtaining
uniform metal powder density in the regions near the marginal edge
portions of the strip. The retaining action of the sidewalls of the
housing 19 influence the uniformity of metal powder distribution in
the outermost extremities of the combined front. The positioning of
the sidewalls of the housing and the outboard nozzles relative to
the edges of the strip may be utilized in combination to obtain ùni-
form metal powder distribution in the outer transverse portions of
the combined cloud for a wide range of coating weights and strip
speeds with a high efficiency of metal powder utilization.
An experimental apparatus built in accordance with the
principles of the present invention included a belt made of galvan-
ized steel strip having a width of 42 inches and a thickness of
0.22 inch. The belt was mounted with respect to the housing 19 so
that the upper reach of the belt moved through the housing in a
direction from its entry end 20 to its exit end 21 to simulate con-
tinuously moving strip. Four discharge nozzles were positioned inthe entry 20 of the housing 19 above the upper reach of the belt as
shown in Figs 4, 5, and 6. The discharge opening of each nozzle had
a long dimension transversely of the direction of movement of the
belt of 6 inches and a depth dimension of 1/4 inch and adjacent
nozzles, in the plane of their discharge openings, were spaced from
each other by a distance of 2-3/4 inches. Each nozzle was fed with
an aerosol of metal powder and compressed air delivered by a blower
driven by a 3/4 horsepower, 3500 r.p.m. motor. Metal powder consis-
ting of -200 mess Fe-Cr powder having about 85% Cr was controllably
1043186
fed to the inlet of the blowers by a mechanism similar to that
shown in Fig. 3. The experimental apparatus was operated at simu-
lated strip speeds of 10, 30 and 60 feet per minute with the rate
of powder feed to the blowers adjusted to obtain a coating weight
of 15 grams per square foot. The uniformity of the metal powder
coating transversely of the belt was within +15 gm/ft square. Fig.
7 illustrates a typical metal powder distribution obtained. The
values of coating weight which the curve of Fig. 7 is based on were ;
obtained by removing and then weighing the powder deposited on
incremental areas of the belt extending in side-by-side relation
transversely of the direction of movement of the belt. Also, the
experimental apparatus was operated at simulated strip speeds of
10, 30 and 60 feet per minute with the rate of powder feed to the
blowers adjusted to obtain a coating weight of 30 grams per square
foot. The metal powder coating obtained had a uniformity trans-
versely of the belt essentially within a range of +4 grams per
square foot of the desired coating weight of 30 grams per square
foot. Fig. 8 illustrates a typical metal powder distribution
obtained. After the experimental apparatus was calibrated as to
the quantity of ~etal powder introduced into the deposition zone for
different settings of powder feed rate and blower speed and after
the metal powder utilization efficiency was obtained, the experi-
mental apparatus was adjusted to obtain a coating weight of 28
gm/ft squared at a line speed of 25 feet per minute. The powder -
distribution of the coating obtained is depicted in Fig. 9 of the
drawings.
An apparatus embodying the principles of the present
invention for applying metal powder to continuous metallic strip
was constructed in the manner shown in Figs. 1 and 2. The nozzles
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were spaced from eac'n other transversely of the strip material by2-3/4 inches and the discharge opening of the nozzles had a dimen-
sion of 6 inches in a transverse direction and a depth of 1/4 inch.
Each of the nozzles was fed with an aerosol of metallic powder and
compressed air from separate blowers to which metallic powder was
fed by an apparatus similar to that shown in Figure 3. The impeller
of the blowers had a small diameter of 5 inches and a large diameter
of 10 inches and each blower was driven by a 3/4 horsepowér-motor
at 3500 r.p.m. Such apparatus was operated in accordance with the
following examples.
EXAMPLE I
A coil of low carbon aluminum killed strip steel having a
width of 30 inches and a thickness of 0.036 inch and a total weight
of about 9000 pounds, previously cleaned in a conventional mannçr,
was placed on the uncoiler 10 and threaded through the apparatus
past the wetting device 13, through the coating zone 14 and the
furnace 15 to the coiling device 17 and then moved through the line
at a speed of 15 feet per minute. The wetting device wetted the
top surface of the strip with a ferrous chloride solution, a charg- ;
ing voltage of about 20,000 volts was applied to the charging wires
within the coating zone and the furnace 15 was operated at a tem-
perature of 200F.-250F. The motors driving the blowers were set
at about 80% of maximum output and the powder feed motor controls
were set to feed metal powder into the blowers at a rate of about
460 grams per minute in order to obtain a coating of about 35 g/ft2
at a strip speed of 15 feet per minute in view of the metal powder
utilization efficiency of the electrostatic coating process deter-
mined from previous operations. The metal powder consisted of -200
mesh Fe-Cr powder having 73% Cr.
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After a portion of the strip had passed thr~ugh the coat-
ing zone, the line was stopped and the weight of the coating on the
top surface of the strip was measured. This was accomplished by
collecting powder deposited on the strip in ten discrete 9 square
inch areas and then weighing the collected powder. The discrete
areas were located in consecutive side-by-side relation in a three-
inch wide portion of the strip surface extending across the strip
perpendicular to the direction of movement of the strip as shown
in Fig. lOA wherein, as viewed in that figure, the area on the
right was at the edge of the strip adjacent the nozzle 30 and the
area on the left was at the other edge of the strip adjacent the
nozzle 33. The weight of powder collected from each area is indi-
cated on Fig. lOA in grams per square foot. Thereupon the apparatus
was operated to move the strip through the line at a speed of 15
feet per minute until prior to the rear end of the coil passing
from the uncoiler when the apparatus was again stopped and the
weight of the metallic powder coating on the strip again measured.
This was accomplished by collecting metallic powder deposited in
five discrete 18-square inch areas extending transversely of the
strip as shown in Fig. lOB and weighing the powder collected. The
weight of powder collected in eacharea is indicated on Fig. lOB
in grams per square foot. As seen from Fig. lOB the average weight
of the coating across the strip within the three-inch portion of
the strip surface was 36.44 g/ft2 and the coating as measured did
not vary from the average beyond +4 g/ft2. The coated coil of steel
strip was subsequently subjected to a chromizing process and the
chromized strip was found to have a substantially uniform iron-chro-
mium alloy coating.
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EXAMPLE II
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A coil of low carbon aluminum killed strip steel having
a width of 30 inches and a thickness of 0.036 inch with a total
weight of about 9000 pounds, previously cleaned in a conventional
manner, was placed on the uncoiler 10 and threaded through the
apparatus past the wetting device 13, through the coating zone 14
and the furnace 15 to the coiling device 17 and then moved through
the line at a speed of 15 feet per minute. The wetting device
wetted the top surface of the strip with a ferrous chloride solu-
tion and a charging voltage of about 20,000 volts was applied tothe charging wires within the coating zone, and the furnace 15 was
operatea at a temperature of 200F.-250F. The motors driving the
blowers were set at about 80% of maximum output and the powder
feed motor controls were set at values appropriate for obtaining
a coating of 35 g/ft2 at a strip speed of 15 feet per minute as
determined from previous operations of the apparatus. The metal
powder consisted of -200 mesh Fe-Cr powder having 73% Cr.
After a portion of the strip had passed through the coat-
ing zone, the line was stopped and the weight of the coating on
the top surface of the strip was measured. This was accomplished by
collecting powder deposited on the strip in ten discrete 9 square
inch areas and then weighing the collected powder as described in
Bxample I. The weight of the powder collected from each area is
shown on Fig. llA in grams per square foot. In view of the
non-uniformity of the powder weights found in the discrete areas
as shown in Fig. llA, the powder feed rate to nozzle 31 was
slightly increased and the powder feed rate to nozzle 33 was
slightly decreased and the apparatus was thereafter operated to
move the strip through the line at a speed of 15 feet per minute
1(~43186
and again stopped and the weight of coating in the discrete areas
was again collected and weighed to obtain the weights in grams per
square foot as shown in Fig. llB. Thereupon the apparatus was
again operated to move the strip through the line at a speed of 15
feet per minute until prior to the end of the coil passing from the
uncoiler the apparatus was again stopped and the weight of the
metallic-powder coating within 18 inch square areas of the strip
- was measured as described in Example I. The weight of powder
collected on each area is shown on Fig. llC in grams per square
foot. The average weight of the coating across the strip within
the areas measured was 34. 35 g/ft2 and the coating as measured did
not vary from the average beyond +4 g/ft2. The coated coil of steel
strip was subsequently subjected to a chromizing process and the
chromized strip was found to have a substantially uniform iron-chro-
mium alloy coating.
EXAMPLE III
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A coil of columbium treated low carbon str-ip steel having
a width of 32 inches and a thickness of 0~048 inch with a total
weight of about 9000 pounds, previously cleaned in a conventional
manner, was placed on the uncoiler 10 and threaded through the appa-
ratus past the wetting device 13, through the coating zone 14 and
the furnace 15 to the coiling device 17 and then moved through the
line at a speed of 15 feet per minute. The wetting device wetted
the top surface of the strip with a ferrous chloride solution and
a charging voltage of about 20,000 volts was applied to the charging `
wires within the coating zone, and the furnace 15 was operated at
a temperature of 200F.-250F. The motors driving the blowers
were set at about 80% of maximum output and the powder feed motor
controls were set at values appropriate for obtaining a coating of
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35 g/ft2 at a strip speed of 15 feet per minute as determin,ed from
previous operations of the apparatus. The metal powder consisted
of -200 mesh Fe-Cr powder having 73% Cr.
After a portion of the strip had passed through the coat-
ing zone, the line was stopped and the weight of the coating on the
top surface of the strip was measured. This was accomplished by
collecting powder deposited on the strip in eleven discrete areas
and then weighing the collected powder as described in Example I.
The weight of powder collected from each area is shown in Fig. 12A
in grams per square foot. In view of the non-uniformity of the
weight of the powder in the discrete areas as shown in Fig. llA,
the rate of powder fed to the nozzle 30 was slightly increased and
the rate of powder fed to the nozzles 32 and 33 was slightly
decreased, and thereafter the apparatus was operated to move the
strip through the line at a speed of 15 feet per minute until prior
to the rear end of the coil passing from the uncoiler, the apparatus
was again stopped and the weight of the metallic powder coating on
the strip again measured in the manner described in Example I. The
weight of powder collected in each of the areas is shown on Fig.
12B in grams per square foot. The average weight of the coating
across the strip within the three-inch band was 35.7 g/ft2 and the
coating as measured did not vary from the average beyond ~4 g/ft2.
The coated coil of steel strip was subsequently subjected to a
chromizing process and the chromized strip was found to have a
substantially uniform iron-chromium alloy coating.
_
The principles of the present invention may be used to
apply any powder to any strip material providing the powder and the
strip material are so characterized so that the powder may be
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electrostatically deposited on the strip material. The powder may
be of any size providing the particle size of the powder permits
the formation of an aerosol of the powder with compressed gas and
provides a cloud of the powder in the deposition zone. Thus, the
principles of the present invention may be used to apply a wide
variety of metal powder on metallic strip and is not limited to the
depositing of Fe-Cr powder on steel strip as described herein.
Furthermore, the principles of the present invention may be used to
deposit metal powder on both sides of metallic strip such as by
providing similar discharge nozzles on the underside of the strip.
In additio~, the features of the present invention may be used to
uniformly deposit metal powder on metallic strip which is thereafter
processed in a manner different from the process described for
producing a different product.
Accordingly, it is to be understood that the foregoing
description including the specific examples is for the purpose of ~;
description only and not as a definition of the limits of the
invention, reference for the latter purpose being had to the appended
claims.
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